I haven't seen the film version but the earlier Play for Today version was really good with Michael Kitchen playing the Sting role. The film was released before the Play for Today version despite being made six years after because the TV version was banned for 10 years before it was shown.
El Topo
Surreal and totally bizarre western. John Lennon was such an admirer of this film that he persuaded Allen Klein, the Beatles manager, to buy the rights and give it a world wide distribution.
https://youtu.be/6Uqb4Jy0GTg
Salo / Pasolini's The 120 Days of Sodom
Set in 1940s Fascist Italy and loosely based on the Marquis de Sade's book The 120 Days of Sodom.
The is probably the most depraved film I've ever seen. It was released in 1975 three weeks after the murder of its director Pasolini, but then was banned...